1. Field of the invention
The present invention relates to an inkjet head, and more particularly, to a bubble remover for an inkjet head comprising an ink tank, an ink reservoir having a nozzle array, and an ink supply path for introducing ink from the ink tank to the ink reservoir, and a method for removing bubbles thereof.
2. Description of the Related Art
FIG. 7 is a sectional view illustrating a conventional inkjet head and a maintenance mechanism disclosed in, for example, Japanese Patent Laid-open Application No. Hei 5-220970.
First, the inkjet head is described. Numerals 1, 2, and 7 of the figure denote a nozzle array where a plurality of nozzles are provided, an opening for directly sucking ink from an ink reservoir 3, and an ink cartridge as an ink tank, respectively. The ink reservoir 3 has the nozzle array 1 formed of the plurality of nozzles, and is normally filled with ink supplied from the ink tank 7. A numeral 4 denotes an ink supply path for introducing ink from the ink tank 7 to the ink reservoir 3.
Next, the maintenance mechanism is described. A cap portion 8 is detachably attached to the distal end side of the nozzles of the nozzle array 1, and sucks ink via the nozzles from the ink reservoir 3. A numeral 9 denotes a second cap portion for sucking ink via the opening 2 from the ink reservoir 3. Numerals 15 and 16 are solenoid valves for opening and closing suction paths extendedly provided from the first and second cap portions 8 and 9, respectively. A numeral 17 denotes a suction pump for sucking ink via the suction paths from the first and second cap portions 8 and 9.
A conventional inkjet head and a conventional maintenance mechanism are constructed as mentioned in the above. Ink suction ordinarily conducted for maintenance (hereinafter referred to as ordinary ink suction) is carried out by, after closing the solenoid valve 16 leading to the second cap portion 9 and opening the solenoid valve 15 leading to the first cap portion 8, actuating the suction pump 17 to suck ink via the nozzles from the ink reservoir 3, thereby discharging bubbles 19 inside the ink reservoir 3, particularly those generated in the vicinity of the region where the nozzle array 1 is provided on the base side, to the side of the first cap portion 8 together with the sucked ink.
However, the bubbles 19 in the ink reservoir 3 which can not be removed by the ordinary ink suction in the construction mentioned in the above are dealt with by special ink suction described in the following.
First, the solenoid valve 15 leading to the first cap portion 8 is closed, and the solenoid valve 16 leading to the second cap portion 9 is opened. Then, the suction pump 17 is actuated to directly suck ink in the ink reservoir 3 not via the nozzles but through the suction path via the opening 2 and the solenoid valve 16. This special ink suction makes ink in the ink tank 7 continue to flow from the ink supply path 4 through the ink reservoir 3 into the opening 2 during the suction continues. The bubbles 19 in the vicinity of the region where the nozzle array 1 is provided, which is a connecting portion between the ink reservoir 3 and the nozzles, are washed away by the continuous ink flow toward the opening 2, and, eventually, the bubbles 19 are taken out on the side of the second cap portion 9 via the opening 2.
With the conventional construction mentioned in the above, since the special ink suction, which is sucking operation not via the nozzles but from the opening 2 provided on the side of one end of the ink reservoir 3, can be conducted other than the ordinary ink suction for maintenance which is sucking operation via the nozzles, two kinds of ink flows can be generated in the ink reservoir 3. The bubbles 19 generated in or moved into the regions of the ink flows can be washed away by the ink flows.
However, the bubbles 19 generated in or moved into a region out of the two kinds of ink flows mentioned in the above, particularly relatively fine bubbles 19 generated in and attached to the vicinity of the region where the nozzle array 1 is provided on the base side, have strong adhesion. There was a problem that, since it is difficult for the conventional ink flows to wash such bubbles away or separate them from the place where they adhere and they are difficult to float in the ink flows, they can not be easily removed.
Further, since the conventional method requires continuous ink flow in order to remove the bubbles 19, there is a problem of diseconomy, i.e., waste of ink.